Track pin with vented rubber plug

ABSTRACT

An improved method and apparatus are provided for sealing hollow pins which are commonly used as lubricant reservoirs in, e.g., track chain assemblies of crawler tractors, and linkage joints of earthmoving vehicles. One embodiment of the invention comprises a plug of elastomer material which has a lubricant passage axially therethrough, which passage receives an auxiliary plug means for the purpose of obturating the passage as well as causing radial expansion of the elastomer plug into positive engagement with a receiving axial bore in a hollow pin. The auxiliary expansion means takes the form of a screw, a spherical ball, or a headless plug employing a plurality of annular serrations. Another embodiment comprises a spherical ball which is received in a stepped, axial bore of a hollow pin and is retained therein by a Belleville washer. The invention facilitates refilling in the field of the lubricant reservoir contained within the pin.

United States Patent 1191 Boggs et al. 1

[22 Filed:

[ TRACK PIN WITH VENTED RUBBER PLUG [75] Inventors: Roger L. Boggs; DavidJohn Balzer, both of East Peoria; Melvin Haslett, Peoria, all of Ill.

[73] Assignee: Caterpillar Tractor C0,, Peoria, Ill.

Apr. 5, 1973 [21] Appl. No.: 348,064

Related U.S. Application Data [62] Division. of Ser. No. 130,664, April 2, 1971, Pat. No.

Primary Examiner-Richard J. Johnson Attorney, Agent, or Firm-Phillips, Moore, Weisenberger, Lenpio & Strabala- [57] ABSTRACT An improved method and apparatus are provided for sealing hollow pins which are commonly used as lubricant reservoirs in, e.g., track chain assemblies of crawler tractors, and linkage joints of earthmoving vehicles. One embodiment of the invention comprises a plug of elastomer material which has a lubricant passage axially therethrough, which passage receives an auxiliary plug means for the purpose of obturating the passage as well as causing radial expansion of the elastomer plug into positive engagement with a receiving axialbore in a hollow pin. The auxiliary expansion means takes the form of a screw, a spherical ball, or a headless plug employing a plurality of annular serrations. Another embodiment comprises a spherical ball which is received in a stepped, axial bore of a hollow pin and is retained therein by a Belleville washer. The invention facilitates, refilling in the field of the lubricant reservoir contained within the pin.

2 Claims, 8 Drawing Figures PMENTEB JUL 1 5 m4 SHEET 1 0F 2 l TRACK PIN WITH VENTED RUBBER PLUG BACKGROUND OF THE INVENTION An additional object is to afford effective venting means for the reservoir regardless of how supplemental fluid is added.

Another object is the provision of auxiliary plug that serves both as a vent closure and expansion means that is capable of increasing unit loading of the plugs peripheral surface to obtain a maximum holding force whether it be used for a bore disposed axiallyin a pin or radially in the wall of a tubular bushing.

Still another object is the ready accessibility and facility to remove said expansion means for expedient resuch track assemblies by improved metallurgy, factory I sealing and lubricating the joints, and providing such factory-assembled joints in readily-serviced, plug-in cartridge form. Two forms of such sealed and lubricated hinge joints, disclosed in US. Pat. Nos. 3,463,560, and 3,492,054, have proved effective in obtaining increased component life; however, production costs, which must be held to a minimum to assure customer acceptance through maximum product value, have proved to be aproblem.

One problem related to cost reduction is effective and economical sealing of the pin bores used for storing lubricant so vital for improved internal wear of the joints. High manufacturing and service costs resulting from precision machining and machine downtime have precluded use of threaded and pressed-in steel plugs'in the vast quantities of such lubricated hinge pins used by present-day industry. Material cost, time and trouble of removing worn and corroded plugs for track service would be prohibitive and impracticaL-Alternate plugs,

easier to install and service, and made of more economical elastomer material, are applicable because they eliminate the basic problems of metallic plugs which occur due to distortion from heat treatment, permaplenishing of the lubricant supply. I

. Still another object is the provision of an enhanced spherical plug which is removably retained in its operative environment by Belleville retaining means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is-a plan view inpartial cross section of a hinge joint and a portion of a track chain;

FIG. 2 shows a sectional view of a cartridge-type hinge joint; I

FIG. 3 is an enlarged cross-sectional view of a reservoir-type pin with a vent-type elastomer plug and assembled complementing auxiliary expansion plug;

FIG. 4 discloses another spherical-type auxiliary expansion plug;

FIG. 5 is a similar elastomer plug with a headless auxiliar'y expansion plug;

FIG. 6 is an alternate embodiment of the elastomer plug in spherical form with modified retaining means;

I 'FIG. 7 is a'plan view in section of a similar hinge joint wherein thebushing'rather than the pin has an internal lubricant reservoir;

nent seizure of such plugs. and even minute scratches on the plugs, etc., that could result in the loss of lubricant.

However, even though elastomer plugs can be lubricated to facilitate assembly and will subsequently swell I by absorbing contacting oil, they remain susceptible to elevated internal pressures in the lubricant reservoir which could result in the plugs inadvertant expulsion. Because of the plugs uncertain frictional retaining characteristics, supplemental means must be providedto assure its positive retention under all conditions.

SUMMARY AND OBJECTS OF. THE INVENTION I In accordance with the present invention, a simple which also makes possible expedient replenishing of pin lubricant without physical removal of the plug.

It is therefore the object of the present invention to provide economical and effective means of plugging reservoir pins employed-in sealed and'lubricated hinge joints.

typically provided two-piece master track links (not FIG. 8 illustrates the method by which such hinge joints of wrapped and stored track would be filled with lubricating oil.

, DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the track assembly illustrated in FIG. 1 comprises a plurality of groundengaging track shoes 10 each of which are rigidly secured to I I a pair of spaced, parallel, interconnected track links 12 as by a plurality of bolts 14. Each pair of track links 12 is pivotally connected by means of a hollow track pin manner that an articulated track chain is formed. With all track sections coupled by such pin and bushing hinge joints an endless track chain is formed which is trained over a drive sprocket and an idler sprocket dis posed on opposite sides of a tractor (not shown) to afford motivating andsteering means for an effective, crawler-type vehicle. Tracks of the present type are shown) to facilitae assembly and service procedures.

Pin 16 conveniently contains a central cavity 20 that ';is defined by closed end 22 and open end 24 which makes possible a reservoir to contain a supply of lubricant. The lubricating fluid'distributed through radial bores 26 to the highly-loaded, coacting, internallydisposed surfaces 28 of the pin and bushing contributes substantially to extending the service life of these members. Suitable seals 30 are normally provided inthe vicinity of the bushing ends to minimize loss of the viscous lubricating flu'id and to prevent entry of foreign matter into the joints. As previously noted, suitable plug means such as disclosed at 32 are necessarily proinvention are a feasible alternative to metallic plugs.

However, to employ such plugs successfully, supplemental ventingwand retaining means in the form of an auxiliary plug means 34 is provided to obtain increased unit pressure from the resilient plug 32. Increasingthe outward radial force by internally positioned auxiliary plug means assures positive retention of the resilient plug under all environmental conditions including that of increased internal pressure that might occur in the reservoir during operations.

If excessive air or no air at all is provided in the reservoir, some fluid compartments can become highly pressurized during operations and consequently starve critical components of vital lubricant. On other occasions, pressure can expel the sensitive plug seals, allowing discharge of all oil from the reservoir. Air lock can also give faulty initial readings resulting in insufficient lubricant to allow the component to realizeits anticipated service life.

As best shown in F lG. 3, elastomer plug 32 is preferably afforded at least one small-diameter, fulllength axial passage 36 which canbe conveniently sealed by the screw-type auxiliary plug 34 after reservoir has been filled. Passage 36 conventionally facilitatesinitial filling of. the lube reservoir 20 by readily receiving a thin hollow needle whereupon hypodermic injection of the flubricant is accomplished while air is vented out aroundthe needle.

FIG. 2 discloses another type of sealed and lubricated joint in the form of a cartridge hinge joint 36 that has a hollow pin 40 with one integrally attached head 42 and a flanged, retainer cap 44 which is detachably secured by a screw 46 to a link member 48. This type of joint is typically employed in the bucket support linkage of end loaders, and can incorporate at one end of the pin a similar resilient plug means 32 having an auxilaryplug 34 to facilitate servicing of the joint.

Turning now to FIG.3, there is shown in enlarged scale, how plug 32 may be inserted into open end 24 as shown at 32. The auxiliary passage 36 can then receive supplemental fluid lubricant and be subsequently sealed by a relatively coarse-threaded screw or auxiliary plug means 34. These threaded members may be formed of any suitable material including plastic; however, it is desirable that theedges 50 of the threads 52 be rounded because sharp edges can .detrimentally afassembly of the minute ball plugs. Such a tool is as shown at 56 having a stepped end portion. 58. To refill reservoir 20, auxiliary ball plug 54can be displaced by tool 56 such that it is expelled from passage 36 into reservoir 20. The auxiliary ball plug 54 may be made of plastic or metal and would be inexpensive enough to be considered disposable. After the reservoir is refilled in the conventional manner, a new auxiliary ball plug can be installed to obturate the passage.

In FIG. 5, there is shown a headless auxiliary plug 60 that employs a plurality of annular serrations 62 to effect increased outward radial holding force for the resilient plug and its positive retention in same. The advantage of this type plug is that it,'like the aforementioned ball plug, may be simply forced on into the reservoir when refilling of the pin reservoir is required and a new pin can be inserted in its place. In such an operation, service time can be minimized and the member floating about in the reservoir can effectively keep residual compounds of the lube fluid from clogging the radial supply ports. Inexpensive plastic or metal can similarly be used for these auxiliary plugs.

FIG. 6 discloses still another type of spherical reservoir plug 64 that requires a counterbored or stepped axial bore 66 for proper seating. The inner surface of this elastomeric plug will sealingly abut a circumferential shoulder 68 and a close-fitting Belleville washer retainer 70 would be forcefully inserted-in the bore and against the outer surface of the ball to keep the plug in place. The outward expansion of the comically-angled surface of the Belleville washer retainer maintains a one-way locking action. onversely, snapping the retainer into an over-center condition by engaging and pulling it with a thin hooked-end probe will allow removal of the washer and plug.

Turning to FIG. 7, there is represented a modified sealed and lubricated hinge joint wherein a portion of the inner bore of the bushing rather than the pin is relieved to effect a fluid reservoir. In the event the pin plu'g'is not readily accessible or a solid pin is required to afford maximum joint strength, a similar elastomer plug means 72 can be employed to close a radial port plug.

74in a reservoir bushing 76. The plug may be obturated by auxiliary plug means 78. Preferably,'the port would be toward one end of the bushing to prevent the engagement of the drive sprocket from damaging the FIG. 8 illustrates a method by which a track chain using the invention would be conveniently filled with lubricating fluid as it is either wrapped or positioned on its side. Each pin bore would be quickly filled by hose from a central supply and closed with the vented plugs.

' All air trapped beneath the plug is automatically exfect the plug by a drilling or reaming action if the screw should be rotated excessively. Additionally, it is preferable that the root diameters of the screws-be a mini-- 54 of a spherical shape that can be readily installedin; the elastomer plug passage 36 by any suitable impact tool that could be magnetized to facilitate aligning and pelled through the vent passage by displacement as shown at during insertion ofthe plug. Installation of the auxiliary plug would then seal the vent passage. In-

troducing the oil into a pin bore already closed by a vented plug would or could inherently exhaust most of the air in the upper part of the bore simply by placing the tractor on a hillside so that the plugs are in a vertically-elevated condition.

It is to be understood that the foregoing description is merely illustrative of preferred embodiments of the invention and that the scope of the invention is not to a be limited thereto, but is to be determined by the scope ofthe appended claims.

. What is claimed is:

silient plug means abuts while auxiliary retaining means in the form of a washer retainer means fixedly engaged in the outer end of said bore applies inward holding force upon the plug means.

2. The invention of claim 1 wherein the plug means is spherical and is of a diameter to closely fit within the stepped bore, and wherein said washer retainer means is a Belleville washer. 

1. In a hinge joint comprising sealed and lubricated bearing means coupling at least two articulately joined members, said bearing means including a pin, a bushing disposed coaxially on said pin, and a lubricant reservoir for supplying lubricant to the outer surface of said pin, and wherein said lubricant reservoir has means defining an inlet closed by resilient plug means, said lubricant reservoir inlet means in the pin having a stepped bore, said bore step forming a shoulder against which the resilient plug means abuts while auxiliary retaining means in the form of a washer retainer means fixedly engaged in the outer end of said bore applies inward holding force upon the plug means.
 2. The invention of claim 1 wherein the plug means is spherical and is of a diameter to closely fit within the stepped bore, and wherein said washer retainer means is a Belleville washer. 